2019 Chemistry WAEC SSCE (School Candidates) May/June

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Chemistry 1 - Objective Test Questions

The periodic table is an arrangement of elements according to their
1. oxidation number.
2. atomic number.
3. mass number.
4. number of neutrons.
A solid substance with high melting and boiling points is likely to be
1. a covalent compound.
2. a dative covalent compound.
3. an electrovalent compound.
4. a non-metal.
Which of the following metals reacts slowly with cold water?
1. Iron
2. Silver
3. Calcium
4. Potassium
Which of the following elements has the highest ionization energy?
1. Calcium
2. Chlorine
3. Fluorine
4. Magnesium
The bleaching action of chlorine is through the process of
1. hydration
2. hydrolysis
3. reduction
4. oxidation
If 6.5 g of magnesium ribbon reacts completely with hydrochloric acid, how many grams of hydrogen gas would be liberated? Mg_(s) + 2HCi_(aq) → + MgCl_2(aq) + H_2(g) [H = 1.0, Mg = 24.0]
1. 0.54 g
2. 0.70 g
3. 1.08 g
4. 1.40 g
Calcium and magnesium belong to the same group of the periodic table because both
1. are metals.
2. form cations.
3. form colourless salts.
4. have same number of valence electrons.
Which of the following substances is non-polar?
1. Br₂
2. NH₂
3. H₂O
4. HBr
Which of the following pairs of components have the same molecular mass? [H = 1.0, C = 12.0, O = 16.0]
1. Ethene and ethyne
2. Ethane and ethene
3. Carbon (II) oxide and ethene
4. Carbon (IV) oxide and ethyne
When an equilibrium is established between dissolved and undissolved solute, the solution is said to be
1. saturated
2. unsaturated
3. concentrated
4. dilute
How many moles of carbon (IV) oxide contains 16.0 g of oxygen? [C = 12.0,0= 16.0]
1. 0.20 mol
2. 0.25 mol
3. 0.40 mol
4. 0.50 mol
Stoichiometry is based on the law of
1. multiple proportion
2. constant composition
3. conservation of energy
4. conservation of mass
What is the percentage by mass of hydrogen in CH₃COOH? [CH₃COOH = 60]
1. 1.7 %
2. 5.0 %
3. 6.7 %
4. 7.1 %
Which of the following compounds has coordinate bonds in its structure?
1. Al₂Cl₆
2. MgCl₂
3. AgCl
4. NaCl
The name of the compound CH₃C(CH₃)₂CH₂CH₂CH₃ is
1. 2-methyl butane
2. 2, 2-dimethyl butane
3. 2-methyl pentane
4. 2, 2-dimethyl pentane
The properties of a good primary standard include the following except
1. high molecular mass
2. low molecular mass
3. high degree of purity
4. readily available
What is the solubility of a salt X at 25^oC if the saturated solution of the salt contains 0.28 g in 100 cm³ of solution? [X = 56.0 g]
1. 0.05 mol dm^-3
2. 0.10 mol dm^-3
3. 2.60 mol dm^-3
4. 2.80 mol dm^-3
Vinegar is an aqueous solution of
1. hydrochloric acid
2. ethanedioic acid
3. ethanoic acid
4. hydrofluoric acid
Which of the following solutions containing one mole per dm³ of the compound would have the lowest pH?
1. Ethanoic acid
2. Hydrochloric acid
3. Sodium chloride
4. Sodium hydrogentrioxocarbonate(IV)
A sample of air was bubbled into water. The pH of the water slowly changed from 7 to 6. Which of the following gases in the sample caused the change?
1. Carbon (IV) oxide
2. Carbon (II) oxide
3. Nitrogen
4. Oxygen
The most suitable indicator for the reaction between NaOH_(aq) and HCOOH_(aq) is
1. bromocresol.
2. methyl orange.
3. methyl red.
4. phenolphthalein.
Consider the following reaction equation: 2Al(OH)₃ + 3H₂SO₄→+ Al₂CSO₄)₃ + 6H₂O. How many moles of tetraoxosulphate (VI) acid is needed to produce 0.5 mol of aluminium tetraoxosulphate (VI)?
1. 0.5
2. 1.0
3. 1.5
4. 3.0
Which of the following pairs of substances has the highest heat of neutralization?
1. Strong acid and strong base
2. Weak acid and weak base
3. Strong acid and weak base
4. Weak acid and strong base
When quicklime dissolves in water,
1. heat is absorbed.
2. heat is evolved.
3. oxygen is liberated.
4. hydrogen is given off.
If the value of △H is positive for a reaction, it means that the reaction is
1. exothermic,
2. endothermic.
3. spontaneous.
4. slow.
Which of the following compounds is formed by the oxidation of ethanol?
1. C₂H₄CO₂H
2. C₂H₅CO₂H
3. CH₃OH
4. CH₃CO₂H
What is the characteristic of the gas liberated when dilute hydrochloric acid is added to iron (II) sulphide?
1. Turns lime water milky
2. Decolorizes bromine water
3. Gives a pop sound
4. Turns lead (II) ethanoate paper black
An organic compound contains 72% carbon, 12% hydrogen and 16% oxygen by mass. What is the empirical formula of the compound? [H = 1.0, C = 12.0, O = 16.0]
1. C₃H₈O
2. C₆H₁₂O
3. C₆H₁₂O₂
4. C₁₂H₁₂O₁₁
When excess chlorine is mixed with ethane at room temperature, the product formed is
1. 1,2-dichloroethane.
2. 1,2-dichloroethene.
3. 1,1-dichloroethane.
4. 1,1-dichloroethene.
Which of the following reagents could be used to distinguish between propan-1-ol and propan-2-ol?
1. H+/K₂Cr₂0₇
2. 1₂/OH^-
3. CH₃COOH
4. NaCl
If a catalyst is added to a system at equilibrium and the temperature and pressure remain constant, there would be no effect on the
1. activation energy of the reaction.
2. rate of the forward reaction.
3. rate of the reverse reaction.
4. heat of reaction.
Consider the following reaction equation: 3Cl₂ + 2NH₃ → + N₂ + 6HCI. NH₃ is acting as
1. a reducing agent.
2. a dehydrating agent.
3. a drying agent.
4. an oxidizing agent.
The oxidation number of chromium in Cr₂O₇ is
1. +4.
2. +5.
3. +6.
4. +7.
The process by which alkanoic acid reacts reversibly with alkanols is known as
1. saponification.
2. esterification.
3. carboxylation.
4. halogenation.
If the oxidation potential of Mg and AJ are + 2.3 7 volts and + 1.66 volts respectively, then Mg would
1. not replace Al.
2. be replaced by AI.
3. remain in the solution.
4. replace AI.
Consider the reaction represented by the following equation: 2SO_2(g) + O_2(g) ⇌ 2S0_3(g). A decrease in pressure of the reaction would
1. decrease the concentration of SO₂.
2. have no effect on the reaction.
3. shift the equilibrium position to the left.
4. shift the equilibrium position to the right.
In a mixture of gases which do not react chemically together, the pressure of the individual gas is
1. atmospheric pressure
2. vapour pressure
3. total pressure
4. partial pressure
Biotechnology is applied in the
1. treatment of sewage.
2. treatment of water.
3. purification of chemicals.
4. purification of metals.
Which of the following organic compounds has the lowest boiling point?
1. C₆H_14.
2. C₅H_12.
3. C₄H₁₂C.C₄H_10.
4. (CH₃)₃CH.
Consider the reaction represented by the following equation: ${\ce {C2H2 ->[H2] X ->[H2] Y}}$ ${\ce {C2H2 ->[H2] X ->[H2] Y}}$ . X and Y respectively are
1. ethane and ethene
2. ethene and ethane
3. ethyne and ethene
4. ethane and ethyne
Which of the following substances can be classified as heavy chemical?
1. CaOCI₂
2. H₂SO₄
3. AgNO₃
4. CaO
In Boyle's law,
1. T is constant, while P varies directly with V.
2. P is constant, while V varies inversely with T.
3. V is constant, while P varies directly with T.
4. T is constant, while V varies inversely with P.
Which of the following apparatus is not used in volumetric analysis?
1. Pipette
2. Burette
3. Desiccator
4. Conical flask
One of the deductions from Rutherford's alpha particle scattering experiment is that
1. electrons are negatively charged.
2. electrons have negligible mass.
3. nuclei of atoms are positively charged.
4. protons are positively charged.
The atoms ${\ce {^64_29Cu}}$ ${\ce {^64_29Cu}}$ and ${\ce {^{65}_{30}Zn}}$ ${\ce {^{65}_{30}Zn}}$ have the same number of
1. nucleons.
2. electrons.
3. neutrons.
4. protons.
The number of electrons in the 3d orbital of ₂₄Cr is
1. 2.
2. 3.
3. 4.
4. 5.
The method used to collect a gas in the laboratory depends on its I. boiling point. II. density. III. smell. IV. solubility in water.
1. I and II only
2. II and IV only
3. III and lV only
4. I, II, III and IV
Which of the following methods is not used for the separation of mixtures?
1. Chromatography
2. Crystallization
3. Distillation
4. Electrolysis
The group to which elements belong in the periodic table is determined by the number of
1. electrons.
2. core electrons.
3. valence shells.
4. valence electrons.
Kipps apparatus can be used to prepare
1. H₂
2. NH₃
3. O₂
4. H₂S

Chemistry 2 - Theory Questions

Section A - For All Candidates

1. State the conditions necessary for the cracking of long-chain hydrocarbons to produce more gasoline.
2. State two reasons why metallic objects are electroplated.
3. 1. Explain briefly why calcium oxide cannot be used to dry hydrogen chloride gas.
  2. State one drying agent for hydrogen chloride
4. Concentrated trioxonitrate (V) acid was added to a solution of iron (II) tetraoxosulphate (VI) and the mixture heated. The mixture turned from pale green to yellow with the evolution of a brown gas. Explain briefly these observation.
5. 1. Write the equation for the reaction between zinc oxide and (I) dilute tetraoxosulphate(VI)acid (II)sodium hydroxide solution
  2. State which property of zinc oxide is shown by the reactions in 1(e)(i).
6. Two isotopes of chlorine are ${\ce {^{35}_{17}Cl}}$ ${\ce {^{35}_{17}Cl}}$ and ${\ce {^{37}_{17}Cl}}$ ${\ce {^{37}_{17}Cl}}$ . State one:
  1. similarity;
  2. difference between the isotopes.
7. State the two products formed when chorine water is exposed to sunlight.
8. Consider the reaction represented by the following equation: ${\ce {H2O + SO2 ->[{H+}] S + H2O.}}$ ${\ce {H2O + SO2 ->[{H+}] S + H2O.}}$ State the:
  1. species that is undergoing oxidation.
  2. oxidizing agent
9. what is meant by carbon-12 scale ?
10. State two properties of a chemical system in equilibrium.

Section B

1. A hydrocarbon having the formula C₁₀H₂₂ was cracked to produce C₆H₁₄ and another hydrocarbon P.
  1. Give the molecular formula of P.
  2. Draw the structure of two isomers of P
  3. Give a reason why P could be polymerized
2. State the guiding principles which are used to explain the way electrons of the atoms of the elements are arranged in atomic orbitals.
3. Consider each of the following substances: NaH, H₂, H₂S_, NH₄Cl
  1. Describe the nature of the intermolecular forces holding the units or molecules together in the condensed (liquid or solid) state.
  2. Explain briefly what happens when a sample of each of the substances is added to water.
  3. Write the chemical equations of any reactions occurring or of any equilibria established
4. Element J has the following electron configuration: 1S² 2S² 2P⁶ 3S².
  1. How many unpaired electrons can be found in J?
  2. State whether J would be a good oxidizing or reducing agent.
  3. Give a reason for the answer in 2(d)(ii)
1. In the Solvay process, explain briefly with equations the functions of the following substances:
  1. limestone
  2. ammonia
2. 1. Write a chemical equation for the fermentation of glucose
  2. Explain briefly why a tightly-corked glass bottle filled to the brim with fresh palm-wine shatters on shatters on standing for some time.
3. Consider the following metals: Na, Fe, K, Cu
  1. Arrange the metals in order of increasing reactivity.
  2. Which of the metals will react with cold water?
  3. Which of the metals could form coloured salts?
4. 1. What is a redox reaction?
  2. Identify which of the following reaction equations are redox.
  3. ${\ce {2Na + Cl2 -> 2 Nacl}}$
  4. ${\ce {AgCl + 2NH3 -> [Ag(NH3)2]Cl}}$
  5. ${\ce {C2H2 + H2 -> C2H4}}$
  6. ${\ce {HCl + KOH -> KCl + H2O}}$
  7. ${\ce {2FeCl3 + 2Kl -> 2FeCl2 + 2KCl + I2}}$
  8. Give a reason for each of the answers in 3(d)(ii).
  9. Write the balanced equations of the half reactions for any two of the redox reactions in 3(d)(ii).

Section C - For Candidates in Nigeria, Sierra Leone, The Gambia and Liberia

1. The following reaction scheme is an illustration of the contact process. Study the scheme and answer the questions that follows
  1. Name X and Y.
  2. Write balanced chemical equation for each of the processes I, II, III and IV.
  3. Name the catalyst used in process II.
  4. Using Le Chatellier's principle, explain briefly why increasing the temperature would not favour the reaction in II
  5. State two uses of SO₂
2. Consider the following reaction equation: 2H_2(g) + O_2(g)→ 2H₂O_(g). Calculate the volume of unused oxygen gas when 40 cm³ of hydrogen gas is sparked with 30 cm³ of oxygen gas.
3. Calcium carbonate of mass 10 g was heated until there was no further change.
  1. Write an equation for the reaction which took place.
  2. Calculate the mass of the residue.
  3. Calculate the volume of the gas evolved at s.t.p.
  4. What would be the volume of the gas measured at 15^o C and 760 mm. Hg? [C = 12.0, O = 16.0, Ca= 40.0, molar volume of a gas at s.t.p. = 22.4 dm³]
1. 1. Draw and label a diagram to illustrate the preparation and collection of dry chlorine gas in the laboratory. Draw and label a diagram to illustrate the preparation and collection of dry chlorine gas in the laboratory.
  2. State two uses of chlorine
2. Describe the preparation of hydrogen from water gas.
3. 1. Name of chief ore of aluminium.
  2. Why is the ore purified?
  3. Name the electrode used in electrode used in electrolysis.
  4. Give one reason why cryolite, NaAIF₆ is added to the electrolyte.
  5. Name three products obtained directly from the destructive distillation of coal.

Chemistry 3 - Practical Questions

All your burette readings (initials and final) as well as the size of your pipette must be recorded but no account of experimental procedure is required. All calculations must be done in your answer booklet. A is a solution containing 15.8 g dm^-3 of Na₂S₂O₃. B was obtained by dissolving 9.0 g of an impure sample of I₂ aqueous K1 and the solution made up to 1 dm^-3_.
1. Put A into the burette and titrate it against 20.0 cm³ or 25.0 cm² portions of B. Use starch solution as indicator. Repeat the titration to obtain concordant titre values. Tabulate your results and calculate the average volume of A used. The equation for the reaction involved in the titration is: I₂ + 2S₂O₃^2- →2I + S₄O₆^2-
2. From your results and the information provided, calculate the:
  1. concentration of A in mol dm^-3
  2. concentration of I₂ in B in mol dm^-3
  3. percentage by mass of I₂ in the sample.
3. Give reasons why the starch indicator was not added to the titration mixture at the beginning of the titration. [O = 16.0 Na = 23.0. S = 32.0, I = 127.0]. Credit will be given for strict adherence to the instructions for observations precisely recorded and for accurate inferences. All tests, observation and inferences must be clearly entered in the booklet in ink at the time they are made.
C isa mixture of two inorganic compounds. Carry out the following exercises on C. Record your observations and identify any gas(es) evolved. State the conclusions you draw from the result of each test.
1. Put all of C ina boiling tube and add about 10 cm³ of distilled water. Shake thoroughly and filter. Keep both the residue and the filtrate.
2. 1. To about 2 cm of the filtrate add a few drops of silver trioxoitrate (V) followed by dilute HNO₃.
  2. Add excess NH₃ solution to the resulting mixture in 2(b)(i).
3. 1. Put the residue in a test tube, add about 2 cm³ of dilute HCl and shake.
  2. Add NH₃ solution in drops to the mixture from 2(c)(i) and then in excess.
1. State what would be observed when BaCl₂ solution is added to a portion of a saturated Na₂CO₃ followed by dilute HCl in excess.
  1. A gas Q decolorized acidified KMnO₄ solution. Suggest what Q could be
2. Name one substance used in the laboratory for drying each of the following substances:
  1. ammonia gas
  2. carbon(IV) oxide
3. Give a reason why a given mass of sodium hydroxide pellets cannot be used to prepare a standard solution.